World number 107 Henri Laaksonen sprung a surprise on Shenzhen Open seventh seed Joao Sousa as the Swiss claimed a 6-3 6-0 first-round triumph on Tuesday.
Laaksonen booked a meeting with Marius Copil after reeling off nine games on the bounce to leave his Portuguese opponent stunned.
Copil endured a much tougher challenge against Malek Jaziri, but dug deep to prevail 6-4 3-6 6-3.
Alexandr Dolgopolov, seeded fifth and a winner in Buenos Aires this year, beat Lloyd Harris 6-3 6-4, while eighth seed Donald Young saw off teenager Nicola Kuhn 7-5 7-6 (7-4).
The Ukrainian now faces compatriot Sergiy Stakhovsky, who defeated Nicolas Kicker in straight sets.
Elsewhere in the draw, there were wins for Evgeny Donskoy, Lukas Lacko and Zhang Zhizhen.
There were contrasting fortunes for the two seeds in action at the Chengdu Open.
While sixth seed Kyle Edmund was a comfortable 6-4 6-2 winner over Bernard Tomic, Serbia's Viktor Troicki (7) suffered a 6-3 2-6 6-2 reverse to Nikoloz Basilashvili.
-- ATP World Tour (@ATPWorldTour) September 26, 2017
Denis Istomin, Guido Pella, Dusan Lajovic and Lu Yen-hsun all enjoyed straight-sets victories, while 2006 Australian Open finalist Marcos Baghdatis won in thee against Vasek Pospisil.
The pick of the second-round ties sees top seed Dominic Thiem face Pella.